The present invention relates generally to downhole subassembly systems and, more particularly, to an orientable whipstock assembly used to orient a whipstock to a desired circumferential location.
Hydrocarbons can be produced through relatively complex wellbores traversing a subterranean formation. Some wellbores can include multilateral wellbores and/or sidetrack wellbores. Multilateral wellbores include one or more lateral wellbores extending from a parent (or main) wellbore. A sidetrack wellbore is a wellbore that is diverted from a first general direction to a second general direction. A sidetrack wellbore can include a main wellbore in a first general direction and a secondary wellbore diverted from the main wellbore in a second general direction. A multilateral wellbore can include one or more windows or casing exits to allow corresponding lateral wellbores to be formed. A sidetrack wellbore can also include a window or casing exit to allow the wellbore to be diverted to the second general direction.
The casing exit for either multilateral or sidetrack wellbores can be formed by positioning a casing joint and a whipstock in a casing string at a desired location in the main wellbore. The whipstock is used to deflect one or more mills laterally (or in an alternative orientation) relative to the casing string. The deflected mill(s) machines away and eventually penetrates part of the casing joint to form the casing exit in the casing string. Drill bits can be subsequently inserted through the casing exit in order to cut the lateral or secondary wellbore.
Lateral wellbores are usually drilled from the parent wellbore in a predetermined direction configured to maximize hydrocarbon recovery. In such installations, it is necessary to form the window at a predetermined circumferential orientation relative to the parent casing. In order to properly position and rotationally orient the whipstock such that the window is milled in the desired direction, a latch assembly associated with the whipstock is extended and anchored into a latch coupling installed or otherwise interconnected in the casing string. The latch assembly typically includes a plurality of spring operated keys, each of which have an anchoring and orienting profile that is received in a mating profile defined internally within the latch coupling. As a result, when the latch assembly is operatively engaged with the internal profile of the latch coupling, the latch assembly and the uphole equipment associated therewith may be anchored and rotationally oriented to the desired direction within the casing string.
A significant amount of well planning goes into properly orienting the latch assembly and whipstock before they are introduced into the wellbore. Nonetheless, it has been found in some cases that operative engagement of the latch assembly with the latch coupling sometimes fails to place the whipstock into correct alignment with the desired rotational orientation. In such cases, the whipstock is secured in the incorrect orientation and otherwise not able to rotate independently to correct the misalignment. Instead, in some cases, the whipstock must be returned to the surface and realigned for an additional trip into the wellbore. As can be appreciated, such corrective actions require a significant amount of time and expense, and it would be advantageous to forgo such remedial efforts.